Printing devices, for printing in legible form on paper a human-readable image specified to the printer by a stream of digital signals, are very well known in the prior art. The present invention is embodied in a printer such as the one described in U.S. Pat. No. 4,796,066, Jan. 3, 1989 (hereinafter, "the Morris patent").
Malfunctions and degradations may occur in such printing devices, resulting in unacceptably poor printed output. In the prior art, it is incumbent upon an operator to visually assess the quality of the output in order to verify correct function, and to direct the system to reprint jobs that were unacceptable. This requires close attention by the operator, and results in lost time and reduced system efficiency when it is necessary to reprint jobs. The longer it takes for the operator to detect incorrect operation, the more such jobs must be reprinted.
The present invention overcomes these drawbacks of the prior art by providing a printer with means for monitoring and maintaining the quality of its own output, informing the operator of trends in the operation that may alert him to the need to service the printer, automatically reprinting defective pages, and assisting the operator in "job reconciliation"--replacing particular defective pages in a job with reprinted pages to produce completed documents possessing integrity.
It is thus a general object of the present invention to provide improved data printers.
It is a particular object of the present invention to provide data printers with self-monitoring, self-correction, and automated job reconciliation.